NLANR's IRCache Project, is funded by the National Science Foundation and others to develop caching protocols, techniques and services. IRCache operates a number of production caches throughout the U.S., which anyone can use. They also develop and maintain Squid, the free caching software for Unix. IRCache's Web Polygraph is a de-facto standard tool for running benchmarks, and their semi-annual Bake-off events provide a forum for fair and rigorous competition among caching products.
DESIRE is a collaboration of institutions from the Netherlands, Norway, Sweden and the UK. Their Caching Project promotes and educates people about Web caching through workshops, reports, and presentations. Team members are very active in TERENA'a TF-CACHE taks force, and the IETF's WREC working group.
TERENA's TF-CACHE task force aims to promote and disseminate information as well as to coordinate development and deployment of network caching technologies throughout the European Research and Education Networking Community and beyond. Members meet regularly to discuss ideas, issues, projects, and products relating to Web caching. The TF-CACHE group has sponsored a number of excellent tools and utilities to assist cache administrators.
The University of Manchester and Loughborough University operate the National JANET Web Caching Service for the UK Academic and Research Community. Their project is an excellent source of information. Here you can find tips on configuring browsers, configuring caches, and a large amount of statistical data.